This invention relates to a three-phase alternating current coil and particularly to a three-phase flat coil having flat coil windings for three-phase alternating current for use in, for example, a printed circuit motor or a three-phase alternator.
Hitherto, in three-phase alternating current coils, a coil winding for one has been wound in an opposite direction to that of the remaining two coil windings for simplifying the end treatment or working. FIG. 1 is a winding diagram of a conventional three-phase alternating current coil in which a coil winding for a phase b is wound in an opposite direction to coil windings for phases a and c to provide a close arrangement of their positive and negative terminals in the end treatment or working.
In order to provide a printed coil formed by such a conventional winding method as shown in FIG. 1, however, there are disadvantages that because of the opposite winding direction of the coil winding for the phase b this coil winding intersects the coil windings for phases a and c at portions X, and thus electrical insulation has to be provided at the portions X.
Specifically, references 1 to 12 shown in FIG. 1 designate coil portions. When printed coils are employed slots or groves for containing the coils are not required, which is different from devices with ring like cores. For simplification, however, the disposition of coil portions corresponding to the numbers 1 to 12 will be refered to as slot numbers hereinbelow.
Typically, printed coils are arranged in a circular disc configuration as shown in FIG. 8. However, FIG. 1 illustrates the printed coil schematically in an elongated arrangement to simplify understanding. Therefore, a line L.sub.1 --L.sub.2 shows an outer periphery of an effective area of the disc-like printed coil, and a line L.sub.3 --L.sub.4 shows an inner periphery of the effective area of the coil.
In FIG. 1, a coil portion P1 is provided on a front side of the disc-like winding and loops around at the inner periphery thereof so that a portion P2 extends on a back side of the disc.
In this way, portions P3 and P4 are also provided on the front side of the disc-like winding, and portions P5 and P6 are on the back side thereof.
In this case, a coil portion P7 disposed at a noneffective area on the inner periphery is on the front side, and a portion P8 is on the back side. A portion P9 is on a boundary between the front and back sides and passes through an inner periphery L.sub.5 of the disc of FIG. 8.
As described above, there are portions provided on the front and back sides. In FIG. 1, the portions provided on the front side are referred to by (O), and the portions provided on the back side are also referred to by (B).
It is thus apparent that there are intersections X at which two front winding portions intersect with each other or two back winding portions intersect with each other. Such portions have to be formed in three-dimensional intersections to provide electrical insulation therebetween, but such insulation is difficult and the size is become large and bulky.
Moreover, the wiring arrangement of FIG. 1 must have the intersections X dispersed throughout the inner and outer peripheries of the printed coil.
To solve this problem, it is possible to use a winding (magnet wire) having an insulating coating thereon, but this will render the intersections thick in size and make it impossible to manufacture a thin, flat printed coil.
To overcome these problems, the present invention provides a three-phase flat coil in which such intersections are minimized and the reduced intersections are collectively provided at substantially one point or in a far smaller area. The intersections have a solid and firm insulating construction to allow easy manufacture. To increase the output, a plurality of coil discs may be overlapped in layers. Easy connections are provided between the coil discs to simplify manufacturing.
In one aspect of the present invention, a three-phase flat coil includes coil portions each having output terminals constituting winding-in and winding-out portions on an outer periphery of an insulating plate and an electrical conductor positoned radially on front and back sides of said insulating plate and having bent-over portions on outer and inner peripheries thereof. Three-phase coil windings including a-phase, b-phase and c-phase windings are each wound in a wave form in the same direction. Ends of the b-phase winding at the output terminals are different in polarity from ends of the a-phase and c-phase windings to form an aggregation of the coil portions. A bridging wiring member, including all necesssary intersections, is provided for the three-phase coil windings. The intersections are and collectively positioned at substantially one point of the outer periphery of said insulating plate. In the bridging wiring member these intersections three-dimensionally intersected with one another and the windings are connected to the respective a-phase, b-phase and c-phase coil windings. Therefore, the bringing wiring member having the intersections is not located on the inner periphery of the insulating plate and is not disposed dispersedly on a plurality of points of the peripheries thereof. Instead, the member is collectively provided only at substantially one point of the outer periphery of the insulating plate thereby rendering the manufacture and wiring arrangement much easier.
Thus the present invention provides a three-phase coil in a generally flat and thin form, even if the size of the bringing wiring member is increased.
As a result of these features the air gap or the like of the magnetic circuit of a rotary electric machine, incorporating a three-phase thin and flat coil according to the present invention is reduced to minimize the magnetic resistance and increase the output.